Anatomical correlation of a well-functioning access graft for haemodialysis

While it is widely accepted that vascular access (VA) haemodynamic surveillance should be performed, its real benefit has not yet been established. In addition, controversy still reigns over pre-emptive angioplasty of detected significant VA stenosis. This pilot study was designed to question the rationale of our decision-making process in VA management.

All 12 adult patients at our centre, dialyzed through a PTFE graft for over 3 months and meeting the clinical and haemodynamic criteria of a well-functioning VA [dynamic venous pressure (DVP) <150 mmHg and VA flow (Qa) measurement >800 ml/min], were prospectively selected. The selected patients underwent a baseline diagnostic angiogram at consent. No patient was submitted to endovascular intervention, including those with stenosis. Close clinical and haemodynamic follow-up monitoring were maintained over the next 6 months, using monthly Qa measurement through a haematocrit dilution (optodilutional) technique to record any access morbidity.

The baseline diagnostic angiogram of the 12 patients revealed at the venous anastomosis: (i) stenosis reducing >75% of the access lumen in three cases; (ii) stenosis of 50-75% in two cases; (iii) stenosis of 25-50% in four cases and (iv) no stenosis in three cases. One patient with stenosis >75% and another with stenosis between 25 and 50% had graft thromboses during the follow-up period. Neither graft thrombosis could have been predicted from the previous month's Qa evaluation. All four patients with a stenosis >50% and who did not thrombose had a normal Qa at the end of the follow-up period.

Our data suggest that the presence of what we call a significant stenosis does not necessarily correlate with measured Qa and might not be associated with early thrombosis deserving immediate intervention. Further studies are needed to clarify the best surveillance protocol and the role of pre-emptive intervention in significant stenosis.